One of the most important electrosurgical operations is in cautery. Cautery is best performed using bipolar electrosurgical apparatus. Two active electrodes forming, for example, the tips of a pair of forceps, are used to grasp a cut blood vessel. Pressure is applied to the forceps to close the vessel, and radio frequency (RF) power is applied to the electrodes to seal the vessel. In electrosurgical cauterisation, the optimum amount of RF power is that which is the minimum which causes the blood vessel to be sealed.
It is current practice for both the level and duration of application of RF power to be controlled by the operator. Different surgeons tend to use different power settings and different coagulation end-points. There are no standards relating to the power-time envelope that should be used on a particular size of blood vessel, and consequently optimum levels of electrosurgical energy are rarely used in practice. Generally, it is the colour of the cauterised vessel which is used by the operator to judge when the right degree of cauterisation has been achieved. Some operators choose to cauterise to an off-white colour whereas others prefer to cauterise to the extent that the vessel is blackened. In both cases the speed of cautery is limited by the reaction time of the operator in switching the RF power source off. This factor also limits the maximum amount of RF power which may be applied, since the coagulation end-point depends on both the period of power application and the power level. The higher the power level, the faster the colour of the vessel changes and the more difficult it is to achieve the optimum degree of cauterisation.